ICECUBE

ICECUBE &
Limits on neutrino emission from
gamma-ray bursts
IceCube collaboration
Journal Club talk 4.15.2011 Alex Fry
Outline
• Neutrinos: The little neutral particles which
are just right for exploring the universe.
• IceCube: A detector for neutrinos.
• Gamma-Ray Burst model constraints from
IceCube
• Conclusions
Neutrinos
• Neutrinos are leptons like electrons, but
neutrinos interact only via the weak force
• Neutrinos come in three flavors: electron,
muon, and tau
• Neutrinos have a small, but nonzero mass
• Neutrinos are created prodigiously by the Sun
(70 billion per second per square cm on Earth)
and other nuclear reactions in the Universe.
Neutrinos are special
Parts of the universe are inaccessible for study
using other types of cosmic rays:
• protons do not carry directional information
because they are deflected by magnetic fields
• neutrons decay before reaching the earth and
high-energy photons are absorbed
• high-energy photons are absorbed
Neutrino mixing
• Neutrinos change ‘flavors’ and so can be any
of the three types
• For example, the T2K experiment being
worked on by some people here at UW will
measure the mixing from νμ to νe by
leveraging the mixing as a function of distance
Neutrino sources
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Supernovae
AGN
Cosmic Ray collisions in Earth’s atmosphere
Cosmic Neutrino Background from Big Bang
Dark Matter annihilations
Gamma-Ray Bursts
IceCube
IceCube is at the Amundson-Scott South Pole Station.
Each photomultiplier is enclosed in a transparent pressure
sphere, a Digital Optical Module (DOM). The DOM also
contains a digitally controlled high voltage supply to power
the photomultiplier, an analog transient waveform digitizer
and LED flashers.
DOMs measure the arrival time of every photon to an
accuracy of better than 5 nanoseconds.
They cost about $350 each for a total cost of 1.7 million for
the DOMs alone.
Detecting Neutrinos in Ice
electron neutrino creates an electron,
the muon neutrino a muon, and the
tau neutrino a tau lepton.
Detecting Neutrinos in Ice
Cherenkov light
electromagnetic radiation is emitted when a
charged particle passes through a dielectric
medium at a speed greater than the phase
velocity of light in the medium
Muon events are
most easily detected
because the muon
travels for a long time
(much further than
the Cherenkov light
in the ice)
IceCube
Icecube also uses
surface detector
modules to help
reject cosmic ray
showers from
above.
In this paper 160
million events
detected and
99.9% were
rejected.
IceCube Neutrino Science
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Ice properties
Gamma-Ray Bursts
Diffuse neutrino backgrounds
Extremely high energy astrophysics
Dark matter, WIMPS
Supernova monitor
Relativistic magnetic monopoles
Gamma-Ray Burst Constraints
• Gamma-ray bursts are one of the few plausible
candidates for ultra-high energy cosmic rays.
• Long duration GRBs (>2 s) are thought be collapse
of massive stars into BH and short duration GRB
(<2 s) are thought be merger compact objects
• Both events are consistent with the fireball model
and producing lots of high energy cosmic rays and
neutrinos.
Gamma-Ray Burst Constraints
The fireball model:
• Mass rapidly accretes onto the newly formed
black hole.
• A highly relativistic outflow/fireball dissipates
energy via synchrotron or IC (electrons)
• Radiation emitted in Kev-Mev range is seen as
the gamma-ray signal (energy 1051 to 1054 erg)
Gamma-Ray Burst Constraints
The fireball model continued:
• Protons are also accelerated via the Fermi
mechanism with an energy spectrum E-2 and
energy=1020 eV (Waxman 1995).
• The protons interact with the Mev photons and
create other particles (Δ+ to pions) and ultimately
neutrinos in the ratio (1:2:0 for νe:νμ:ντ).
• Thus high energy cosmic rays and neutrinos
(which arrive at earth in the ratio 1:1:1) are
plausibly explained by GRBs.
Gamma-Ray Burst Constraints
So IceCube should be able to detect GRB’s
Sensitivity of the IceCube detector to astrophysical sources of high energy muon
neutrinos. Ahrens et al. 2004
Gamma-Ray Burst Constraints
Thin lines - 41 selected neutrino spectra for 41 bursts.
Thick dotted line - standard Waxman spectra for single burst.
Thick solid line – sum of all
Thick dashed lined – sum of 41 Waxman like spectra.
Gamma-Ray Burst Constraints
IceCube has found no evidence for
neutrino emission excluding
prevailing models at 90%
confidence.
Conclusions
• In the coming years data will improve and
better constraints will be had. Stay tuned.
• But where are the missing neutrinos?
Emperor Penguins
• Emperor Penguins are endemic to Antartic
costal regions.
• An Emperor Penguin can hold its breath for 20
minutes, and dive to depths of over 550 m
(1/5 the depth of IceCube).
• Emperor Penguins are awesome.
ref
• Search for muon neutrinos from Gamma-Ray
Bursts with the IceCube neutrino telescope
IceCube Collaboration: R. U. Abbasi, et al
• Sensitivity of the IceCube detector to
astrophysical sources of high energy muon
neutrinos. Ahrens et al. 2004